Civil-rights attorneys are suing to end what they call "suspicion-less searches," which they believe take place at every U.S. border and airport. From October 2008 through June 2010, they found, agents went through the electronic gadgets of more than 6,500 people, including 3,000 U.S. citizens.

One of them was Islamic studies doctoral student Pascal Abidor of Brooklyn, who was detained in July at Newark Liberty International Airport. Authorities asked whether he was Muslim, how he had paid for his travel, what he intended to do professionally and how he got along with his girlfriend. They also asked about a previous stop in May, on the U.S.-Canadian border, where agents handcuffed him, demanded his computer passwords and took his laptop, containing his coursework, e-mail, tax returns, photos and search-engine history, according to the lawsuit.

“I haven’t done anything wrong,” Abidor said in a phone interview today from McGill University in Montreal. “Every answer I gave was rational, truthful and reasonable. They wanted more.”

It appeared, Abidor said, that authorities were trying to determine whether he had any connection to terrorist organizations.

Abidor filed suit Wednesday in U.S. District Court in New York along with two professional organizations whose members, a photojournalist and a defense lawyer, were subject to similar searches. They claim that the practice, dating to Bush administration policy from 2008, violates free-speech and search-and-seizure rights, and asks that such searches no longer take place.

“It isn’t something that most people know about,” said Michael Price of the National Association of Criminal Defense Lawyers, an attorney for the plaintiffs. “It really does impact every American and every person traveling in this country. No matter how you feel about having your gas tank taken apart or having your luggage rifled through by Customs, there’s a completely different sense of your privacy being violated when that search extends to the private details of your life stored on your laptop computer.”

Matthew Chandler, a spokesman for the Department of Homeland Security, said he could not comment on pending litigation.

“Searches of laptops and other electronic media during secondary inspection are a targeted tool that [U.S. Customs and Border Protection] uses in limited circumstances to ensure that dangerous people and unlawful goods do not enter our country,” he said in an e-mailed statement.

The search policy, as well as a privacy assessment, is available at DHS.gov, he said.

Less than one-tenth of 1 percent of travelers undergo such searches, according to department statistics.